FR2842147A1 - DRIVE CHAIN HAVING A GEAR CHANGE MECHANISM INTEGRATED IN A WHEEL - Google Patents

Abstract

The chain includes an arrangement having a dog clutch (46) with a neutral position between gear ratios. The dog clutch provides direct engagement between an input shaft and one of two gearwheels, and has a mechanical transmission path between the input shaft and the other gearwheel with a reduction ratio different from the direct engagement. The two gearwheels are permanently meshed with a rotating toothed wheel (3). The input shaft is coupled with the shaft of an electric motor (M). An Independent claim is also included for a process for controlling gear ratio changes.

Description

The present invention relates to motor vehicles with traction

  electric. It concerns both purely electric vehicles and hybrid type vehicles,

  especially hybrid series vehicles.

  In certain embodiments mentioned above, the drive wheel (s) of these vehicles are only driven by an electric motor. In this case, it is possible to integrate an electric traction motor directly into a wheel, rather than installing it on the chassis of the vehicle, which makes it possible to remove the drive shaft. In addition, one of the advantages in itself of the electric traction is due to the constant character of the torque which is capable of developing an electric motor over the entire range of rotational speed. Of course, to take full advantage of the configuration mentioned (electric traction motor integrated in a wheel), it is desirable to be able to create ground connection assemblies as compact and as light as possible. In particular, it is desirable that the traction chain in itself, going from the electric motor to the wheel, be as light and

  compact as possible, especially since it is unsprung masses.

  It has already been recalled that electric motors are capable of developing fairly large and substantially constant torques over the entire speed range. However, we also know that the size of an electric motor is substantially proportional to the torque for which it is designed. Also, to have as large a torque at the wheel as possible while having a very compact electric traction motor, it is desirable to install the greatest possible total reduction between the motor shaft.

wheel axis.

  If we increase the total reduction installed between the shaft of the electric motor and

  the axis of the wheel, the engine speed is also increased to the maximum vehicle speed.

  However, the mechanical and electrical stresses that an electric motor undergoes greatly increase with its speed of rotation. If a maximum limit is set for the rotational speed of the electric motor, it may be desirable to have a choice of total reduction ratios between the electric motor and the wheel. Must therefore

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  also integrate into the wheel a gear change mechanism which allows either

  to obtain a significant torque at the wheel, ie to reach the maximum speed of the vehicle.

  This raises the problem of a design as compact as possible of such a gearshift mechanism, so as not to lead to a solution overall (that is to say electric motor plus gearshift mechanism) more penalizing in terms of space and weight that an electric motor in direct drive, dimensioned to be able to develop on the wheel axis the maximum torque that is sought by increasing the final reduction. It is also necessary to design a control system making it possible to switch from one report to another in as simple and rapid a manner as possible. And it takes the means to go from one

  compared to each other do not weigh down the entire chain of transmission.

  The invention provides a traction chain for a motor vehicle, comprising 15. a wheel carrier supporting a rotary hub intended to receive a driving wheel and materializing an axis of rotation for said driving wheel, * a rotary toothed wheel, having the same axis of rotation as the axis of rotation of said driving wheel, the toothed wheel being in direct engagement with the hub, * an arrangement comprising at least two pinions permanently engaged with said toothed wheel, comprising an input shaft intended to be coupled with the shaft of an electric motor, and comprising a gearshift mechanism with neutral between gears, said mechanism comprising a direct connection between the input shaft and one of the pinions, said mechanism comprising, between the input shaft and the other of the pinions, at least one other mechanical

  transmission with different gearing from direct drive.

  In a more particularly advantageous implementation, the invention provides a gear change mechanism comprising a dog clutch making it possible to select one or the other of the gears. Advantageously, said mechanism is devoid of any friction clutch. In other words, it only includes mechanically positive means of engagement. In addition and preferably, the invention makes use of a brushless, self-piloting synchronous electric motor which, by its nature, comprises a rotor position sensor. The invention uses only this engine position sensor and a

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  -3 sensor assembly associated with the gear change mechanism to determine the rotational speed of the wheel in question and achieve all gear changes

  required. Preferably, the arrangement includes only two reports.

  The invention is illustrated by means of the appended figures, in which: * FIG. 1 shows a vehicle wheel in which the electric traction chain according to the invention is integrated, sectional view along C / C indicated in FIG. 2 * Figure 2 is a view along A in Figure 1; * Figures 3A, 3B and 3C are partial views showing the electromechanical transmission chain; * Figures 4A, 4B and 4C are sections along 4/4 in Figure 2, showing the essential organs of the gear change mechanism in two reports; * Figure 5 is a partial view of the electromechanical transmission chain; ò Figure 6 is a timing diagram showing the evolution over time during the gear changes of the position of the control fork, the speed of the

  traction motor and traction motor torque.

  FIGS. 1 and 2 show a wheel W on which a tire T is mounted. The wheel is rotatably mounted on a wheel carrier K, the axis XX being its axis of rotation. We also see a casing 1 closed by a cover 2 and by the stator part S of an electric traction motor M. The casing 1 has an upper extension 10 and a lower extension 11 at the ends of which a suspension system of the wheel W can be attached relative to a chassis or to the body of the vehicle. We only show

  here that the so-called unsprung bodies of a ground connection for a motor vehicle.

  The casing 1 delimits an enclosed space with the cover 2 and the electric motor M. This enclosed space may contain the quantity of oil necessary to ensure the lubrication of the mechanical members installed therein. Inside the casing 1, there is a toothed wheel 3 (see Figure 1 and Figures 3), rotating around the axis XX, in direct engagement with the wheel W.

  In FIG. 3A, it can be seen that the toothed wheel 3 is meshed with a first pinion 31.

  The first pinion 31 is coaxial and integral with an auxiliary pinion 310 of diameter larger than the diameter of the first pinion 31. The first pinion 31 and the

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  -4 auxiliary pinion 310 form a single rotary mechanical piece. The auxiliary pinion 310 is meshed with an intermediate pinion 6. The pinion 6 makes it possible to

  maintain the same direction of rotation of the electric motor regardless of the gear engaged.

  Furthermore, the toothed wheel 3 is meshed with a second pinion 53. The second pinion 53 is coaxial and integral with a pluggable pinion 530 (see in particular FIG. 3A and FIG. 4A). The second pinion 53 and the interchangeable pinion 530 form a rotary monobloc mechanical part. This mechanical part comprises a peripheral clearance 532 devoid of teeth, adjoining the interchangeable pinion 530 (see in particular FIG. 4A). This mechanical part also includes a smooth intermediate bearing 531. A clutchable idler gear 42 is mounted on the smooth intermediate bearing 531, coaxially with the second gear 53, so as to be able to rotate

  freely relative to the second pinion 53.

  The gear change mechanism includes a dog clutch 46 for selecting a gear. In the illustrated embodiment, the dog clutch 46 has an internal toothing identical to the (external) toothing of the dog clutch pinion 530 and of the dog clutch pinion 42. The dog clutch 46 can be dog clutched either on the dog clutch pinion 42 to have a multiplication ( Figure 3A and 4A), either on the sprocket 530 for direct drive (Figure 3C and 4C), or the dog 46 can be brought into a non-dogged position in which its internal toothing faces the

  clearance 532 free of any teeth (Figures 3B and 4B).

  Furthermore, the dog clutch 46 has an outer peripheral groove 460 and recesses 461 (see FIG. 5). We see a shaft end A (Figures 3 and 4) of the rotor of the electric motor M, the axis YY being the axis of rotation of the shaft A. A bell 38 is mounted integral with the shaft A of the rotor of the electric motor M. The dog clutch 46 is centered by the bell 38. A fork 1 6 is engaged radially from the outside in the peripheral groove 460 fitted on the dog clutch 46. The bell 38 comprises fingers 380 engaged in the recesses 461 of the dog clutch 46. Dog clutch 46 can slide axially by

  relative to the bell, while being integral in rotation thereof.

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  -5 The fork 16 is controlled by a gear motor 12. A position sensor 21 is connected to the fork 1 6. The dog clutch 46 can take three positions: a position in which dog clutch 46 drives the toothed wheel via an intermediate pinion 6 for reversing the speed of rotation; the dog clutch 46 is then clutched with the idler pinion 42, therefore engaged with the first pinion 31, via the intermediate 6 and auxiliary pinions 310 (see in particular FIGS. 3A and 4A); it is said other mechanical transmission path; ò a position in which it is clutched with the auxiliary pinion 530, therefore engaged with the second pinion 53 (see in particular FIGS. 3C and 4C),

  10. a neutral intermediate position, visible in FIGS. 3B and 4B.

  The first pinion 31 and the second pinion 53 are permanently driven by the toothed wheel 3. With identical teeth, they both rotate at the same angular speed. The second pinion 53, when it is engaged with the shaft A of the rotor of the electric motor M via the second auxiliary pinion 530, the ring 42 and the bell 38, is in direct contact with the motor M. On the other hand, when the traction torque passes through the first gear 31, via the bell 38, the dog clutch 46, the idler gear 42, the intermediate gear 6 and the auxiliary gear 310, there is between the shaft A of the rotor of the electric motor M and the first gear 31 a gear ratio corresponding to the ratio R between the number

  auxiliary pinion teeth 310 and the number of idler pinion teeth 42.

  Note also that, if in the said other mechanical transmission path, the dog engages

  the toothed wheel 3 via an intermediate pinion 6 making it possible to reverse the speed of rotation.

  Alternatively (not shown in the figures), it could very well alternatively drive the electric motor in opposite directions of rotation for one gear and for the other gear; in this variant, in said other mechanical transmission path, the dog

  drives the wheel directly, without an intermediate gear to reverse the direction of rotation.

  A gear change implies a significant 'instantaneous' change in the speed of the electric traction motor. When the vehicle is equipped with several driving wheels each equipped with an electric motor and gearbox assembly according to the invention, the change is preferably made in synchronism at least on the wheels of the same

vehicle axle.

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  -6 The timing diagram given in Figure 6 illustrates the sequence of operations. Whatever the direction of the gear change, and whatever the gear change concerned, a gear change involves canceling the engine torque (zone 1), shifting the gearbox to neutral position (zone 2), then involves adjusting the engine speed to the level corresponding to the future gear selected (zone 3), in order to be able to engage

  mechanically said ratio, before piloting the engine again to the desired torque.

  In the timing diagram of FIG. 6, preferential details of embodiments also appear, without limitation. To facilitate shifting, small speed oscillations can be caused by judicious control of the torque of the electric motor (zone 4)

  whose role is to promote the catch of the dogs during the engagement of the next report.

  It should be noted that the variations in torque and the variations in speed involved are very small: the variation in torque shown in zone 4 only serves to accelerate the rotor of the motor M against its own inertia; the resulting variation in speed is itself very small, all the more so since it is immediately limited by the start of engagement of the dog clutch (resumption of functional games). Do not try to compare the variations in torque and speed represented in zone 4 with the variations in torque and speed

  represented in the other zones, the drawing being purely schematic.

  Preferably and if the driving conditions allow it, it is advisable to control the torque of the electric traction motors so that just before releasing a report and

  just after engaging another gear, the torque at the wheel is roughly equivalent.

  If we are going towards a greater total reduction (going from second to first), this requires voluntarily limiting the torque of the electric motor just after the gear change maneuver. The decrease in torque is made appreciably in the R ratio. If we are going towards a smaller total reduction (go from first to second), this requires voluntarily increasing the electric torque just after the speed change maneuver. The increase in torque takes place appreciably in the R ratio. However, the torque available to the engine is necessarily limited to a value Cmax. If the expected increase in torque leads to a value greater than Cmax, it is advisable, before the gear change maneuver, to decrease the torque to a value

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  -7 smaller or equal to Cmax / R, so that after the change of maneuver

  speed, the applied torque does not exceed the value Cmax.

  It should also be noted that, when shifting from one gear to a ratio of lesser total reduction, the electric motor must shift as quickly as possible to a lower speed as soon as the gearbox is in neutral position. It is therefore necessary to electrically brake the motor, which implies being able to absorb electrical energy elsewhere (for example dissipation in resistors or recharging of storage element). In summary, the invention allows * on the 1st gear (large reduction) to take advantage of a significant torque in terms of

  the wheel, so have high dynamic performance.

  * On the 2nd gear (current reduction, around 8) to allow speed to be reached

vehicle maximum.

  * In some cases, consider 2-wheel drive vehicles instead of 4, increasing the starting torque (reduction of the equipment installed, therefore

mass and price).

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Claims (8)

  1. Traction chain for a motor vehicle, characterized in that it comprises ò a wheel carrier (K) supporting a rotary hub intended to receive a driving wheel (W) and materializing an axis of rotation for said driving wheel, * a wheel toothed (3) rotary, having the same axis of rotation as the axis of rotation of said drive wheel, the gear being in direct engagement with the hub, an arrangement comprising at least two pinions (31 and 53) permanently engaged with said gear wheel, comprising an input shaft intended to be coupled with the shaft of an electric motor, and comprising a gearshift mechanism with neutral between gears, said mechanism comprising a direct connection between the shaft of input and one of the pinions, said -mechanism comprising, between the input shaft and the other of the pinions, at least one other mechanical transmission path with gear different from the socket direct.   2. Traction chain according to claim 1, characterized in that the gear change mechanism comprises a dog clutch (46) making it possible to select one or the other reports.   3. Traction chain according to claim 1 characterized in that, in said other mechanical transmission path, the dog clutch (46) drives the toothed wheel via a pinion   intermediate (6) to reverse the speed of rotation.   4. Traction chain according to claim 1 characterized in that, in said other mechanical transmission path, the dog clutch (46) drives the wheel directly, without intermediate gear.   5. Traction chain according to claim 1, characterized in that it is devoid of friction clutch.   6. Traction chain according to claim 1, characterized in that it is two reports only. P10-1470 FR   7. Traction chain according to claim l characterized in that it comprises an electric motor (M), in which the electric motor is of the self-controlled synchronous type, the motor comprising at least one integrated rotor position sensor and used for piloting the engine. 8. Traction chain according to claim 7, characterized in that the only sensors used to determine the speed of rotation of the wheel are said position sensor integrated into the motor and a sensor assembly associated with the mechanism for changing report. PI 0-1470 FR